P0171 and P0172 ???
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Cadillac Catera and Cimarron Forum Discussion, P0171 and P0172 ??? in Past Cadillac Vehicle Discussion; Hi all. I'm new to this forum. I do not own a Caddy, but the folks do, and I'm tryin' ...
  1. #1
    bomkok is offline Cadillac Owners Member
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    P0171 and P0172 ???

    Hi all.

    I'm new to this forum. I do not own a Caddy, but the folks do, and I'm tryin' to work some things out for 'em.

    I'm working on their 2001 Catera Sport with about 56,000 miles. They've only had the car a couple years, and just started having problems recently.

    First...the engine light came on and it was idleing erratically. I disconected the battery to reset the light, and then it would barely run until the engine light came on again(assume entering limp-home mode). Ran it down to the parts store to get a fault read, and it came up with P0300,P0301,P0302,P0303,P0305(genereal and cylinder specific misfires). Rummaged around under the hood for awhile looking for anything obvious and found a vacuum leak. One of the smaller bungs had broke off the directional air valve thats in line between the manifold power brake booster. Replaced the valve and reset the light(batt. discon) and the car was running beautifully......for 3 days.

    Today...got a call, the light came on again. Went to check it out and it idles fine runs great except for a little pinging(detonation) under heavier load(hard throttle or up hill). Ran it back for a code read and getting the seemingly obligitory misfire codes(P0300,P0301,P0303,P0305), except this time only on one bank, if I'm not mistaken. Also getting codes P0171 AND P0172

    The guy at parts store said the codes were System Too Lean, banks 1 and 2 respectively, but when I looked for info on the codes myself, I came up with
    P0171-Fuel Trim System Lean Bank 1
    P0172-Fuel Trim System Rich Bank 1


    I have browsed the archives a bit but haven't found anything displaying both codes and wonder if this could indicate a specific problem.

    The only other background info is the folks had the fuel filter changed about 3 months ago and the guys at the quick-lube place broke the canister cap for the filter and had to replace it.

    Any thoughts on the matter would be much appreciated.

    Thanks.

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  3. #2
    AllenPacla is offline Cadillac Owners Fanatic
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    Re: P0171 and P0172 ???

    Just a few threads below this one, you will see one. Search well dude.

  4. #3
    bomkok is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    Quote Originally Posted by AllenPacla
    Just a few threads below this one, you will see one. Search well dude.
    I've seen that thread and many like it "P0171 and P0174"
    They're pretty straight foward....LEAN condition.

    My dilemma "P0171 and P0172" indicates BOTH rich and lean condition in same bank.

    The search is ongoing, but thanks for your input, anyhow.


    And to edit broken cap condition in original post...spoke to parents to clarify, and turns out it was the oil filter cap that got broke as opposed to fuel.

  5. #4
    meyema03's Avatar
    meyema03 is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    just throwing this out there mass airflow sensor?

  6. #5
    bomkok is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    Quote Originally Posted by meyema03
    just throwing this out there mass airflow sensor?
    I'm leaning away from a MAF problem...I've pulled the MAF and she looks clean as a whistle...gave a good carb cleaner spraydown anyway. The reason I'm thinkin otherwise(aside from clean appearance)...a bad or gummed-up MAF will tend to lead to either a rich or lean condition, as opposed to both. Bad connections within the sensor or the plug should give an error code relating to the MAF(i think). It may be the MAF, but I'd sure like to narrow things down before doin' the "crap-shoot" with $150 parts.

    Went ahead and changed the fuel filter, this evening, and was alarmed that I didn't get sprayed with gas.
    I couldn't find the pressure relief valve(right away) so I pulled the pump relay and tried to start it to bleed off the fuel pressure in the lines. I figured it would run till the pressure dropped in the line. The engine turned over a couple times but didn't even act like it wanted to start, so I assumed some safety feature kept it from starting while the relay was removed. Since I only turned it over for a couple short bursts, I was sure the lines were still pressurized, but when I removed the filter....no gasoline shower.

    After installing new filter, I reset the engine-light, started the car, and it took a long time for the line to repressurize(almost a full minute of the fuel starved sputter-spit). Drove her around a bit and shes running good...light hasn't come back on YET, and I didn't hear any detonation on hard accel(much cooler out this evening, though.)

    Anyway...I fully expect to see the engine-light coming back on, and I'm thinkin maybe my fuel pump isn't running very effeciently...could a bad fuel pump cause the pressure to bleed off while the car sits???

    I put a little gas in it earlier this week...then filled her up after workin on it tonight. Neither time did i hear the "hisss" when removing the cap...isn't there a check valve or something to prevent preessure from bleeding back into the tank(even if the pump is bad)???

    And...is the fuel pump inside the tank on these cars?

  7. #6
    1986cimarron's Avatar
    1986cimarron is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    Document ID# 626887
    2000 Cadillac Catera


    --------------------------------------------------------------------------------

    DTC P0171 Fuel Trim System Lean Bank 1
    Circuit Description
    While in Closed Loop, the engine control module (ECM) monitors the heated oxygen sensor (HO2S) signal voltage and adjusts the fuel delivery based on the signal voltage. A change made to fuel delivery will be indicated by the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in the Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to the fueling in order to re-center and restore control to the Short Term Fuel Trim. The Short and the Long Term Fuel Trim can be monitored with a scan tool. Ideal fuel trim values are around 0 percent. A positive fuel trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition. If an excessively rich or lean condition is detected, the ECM will set a diagnostic trouble code (DTC). The Long Term Fuel Trim diagnostic parameter is an average of several of the long term speed load learn cells which the ECM selects based on the engine speed and the engine load.

    Conditions for Running the DTC
    Closed Loop operation
    Fuel trim enabled
    Conditions for Setting the DTC
    The ECM detects fuel trim values more than 23 percent for long term fuel trim or more than 25 percent for short term fuel trim.

    Action Taken When the DTC Sets
    The ECM will illuminate the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails, if the diagnostic fails under the same conditions, the load, the RPM, the temperature, as the previous ignition cycle that the test ran and failed.
    On the first drive trip that this diagnostic fails, Fail Pending, the information will be stored in the Freeze Frame. Any data that was previously stored in the Freeze Frame will be overwritten by the Freeze Frame data for this DTC. The only exception to this is if a Misfire DTC was already recorded in the Freeze Frame. In this case, the misfire data stays in the Freeze Frame and the fuel trim data is not stored.
    Conditions for Clearing the MIL/DTC

    Important
    If the last fault was during a non-typical driving condition, the MIL may remain ON more than three drive trips. Review the Freeze Frame for the last failure conditions.


    The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes within the same conditions that the DTC last set.
    A History DTC clears after forty consecutive warm-up cycles if no failures report by this diagnostic or any other emission related diagnostic.
    The scan tool clears the MIL/DTC.
    Diagnostic Aids
    Use the J 35616-A connector test adapter kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals. Refer to Using Connector Test Adapters in Wiring Systems.
    If a DTC P0171 cannot be duplicated, the DTC may have been caused by the customer running the vehicle out of fuel.
    If DTC P0174 is also set, this indicates that both banks of the engine are operating lean. Inspect all areas of the engine for a vacuum leak. Also inspect the crankcase ventilation (PCV) system for leaks. Make sure that the engine oil fill cap is tight. Check that the engine oil dip stick is fully seated. A skewed mass air flow (MAF) sensor may be the cause of these DTCs.
    Fuel delivery--A fuel delivery malfunction can cause this DTC to set. Thoroughly inspect all items that cause a lean condition.
    Fuel contamination--Water, even in small amounts, near the in-tank fuel pump inlet, can be delivered to the injectors. The water causes a lean condition and can set a DTC P0171.
    Secondary AIR System--Inspect the AIR system for proper operation and verify that all the components are connected.
    Intermittents--For an intermittent, refer to Symptoms .
    If a repair is necessary refer to Wiring Repairs or Connector Repairs in Wiring Systems.
    Test Description
    The numbers below refer to the step numbers on the diagnostic table.

    This step determines if the fault is present.

    This process may help in order to recreate the malfunction.

    This step determines if both banks are running lean.

    This step addresses areas of concern that could cause both banks of the engine to run lean.

    DTC P0171 - Fuel Trim System Lean Bank 1 Step
    Action
    Values
    Yes
    No

    1
    Did you perform the Powertrain On-Board Diagnostic (OBD) System check?
    --
    Yes? Go to Step 2
    No? Go to Powertrain On Board Diagnostic (OBD) System Check

    2
    Is DTC P1460 set?
    --
    Yes? Go to DTC P1460 Misfire Detected With Low Fuel Level
    No? Go to Step 3

    3

    Important
    If any DTCs are set except P0171 and P0174, refer to those DTCs before proceeding with this diagnostic.


    Connect a scan tool.
    Allow the engine to run at a normal operating temperature.
    Verify that the fuel system is in Closed Loop.
    Monitor the Long Term Fuel Trim for Bank 1 with the scan tool.
    Is the LT FT less than the specified value?
    +23% LT
    Yes? Go to Step 4
    No? Go to Step 5

    4
    Turn ON the ignition with the engine OFF.
    Review the Freeze Frame data for this DTC and note the parameters.
    Clear the DTCs.
    Turn OFF the ignition for 30 seconds.
    Start the engine.
    Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions that are recorded in the Freeze Frame as possible. Refer to Conditions for Running the DTC.
    Check for any DTCs.
    Is this DTC set?
    --
    Yes? Go to Step 5
    No? Go to Diagnostic Aids

    5
    Is DTC P0174 also set?
    --
    Yes? Go to Step 6
    No? Go to Step 7

    6
    Visually/physically inspect the following items:

    Vacuum hoses for splits, kinks, and proper connections. Refer to Emission Hose Routing Diagram for underhood vacuum hose routing diagrams.
    Air induction system after the MAF sensor for leaks.
    Throttle body and intake manifold for leaks.
    Crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Diagnosis .
    Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    ECM and the sensor grounds are clean, tight, and in the proper locations. Refer to Ground Distribution Schematics in Wiring Systems.
    Engine mechanical failure. Refer to Engine Noise Diagnosis in Engine Mechanical.
    Did you find and correct the condition?
    --
    Yes? Go to Step 9
    No? Go to Fuel System Diagnosis

    7
    Visually/physically inspect the following items:

    Bank 1 for exhaust leaks and missing or loose exhaust hardware.
    Bank 1 HO2S 1 is installed securely and the electrical connector is not contacting the exhaust system.
    Engine mechanical failure. Refer to Engine Noise Diagnosis in Engine Mechanical.
    Vacuum leaks that only affect Bank 1 (intake manifold, upper plenum O-rings, injector O-rings, etc.).
    Did you find and correct the condition?
    --
    Yes? Go to Step 9
    No? Go to Step 8

    8
    Test for a malfunctioning oxygen sensor or circuit. Go to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 .

    Did you find and correct the condition?
    --
    Yes? Go to Step 9
    No? Go to Fuel System Diagnosis

    9
    Using a scan tool, clear the DTCs.
    Start the engine.
    Allow the engine to idle until the engine reaches the normal operating temperature.
    Select DTC and the Specific DTC function.
    Enter the DTC number that was set.
    Operate the vehicle within the Conditions for Running this DTC until the scan tool indicates that the diagnostic Ran.
    Does the scan tool indicate that the diagnostic Passed?
    --
    Yes? Go to Step 10
    No? Go to Step 2

    10
    Does the scan tool display any additional undiagnosed DTCs?
    --
    Yes? Go to the applicable DTC table
    No? System OK



    --------------------------------------------------------------------------------
    Document ID# 626887
    2000 Cadillac Catera

  8. #7
    Warez is offline Cadillac Owners Fanatic
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    Re: P0171 and P0172 ???

    Quote Originally Posted by bomkok
    I'm leaning away from a MAF problem...I've pulled the MAF and she looks clean as a whistle...gave a good carb cleaner spraydown anyway. The reason I'm thinkin otherwise(aside from clean appearance)...a bad or gummed-up MAF will tend to lead to either a rich or lean condition, as opposed to both. Bad connections within the sensor or the plug should give an error code relating to the MAF(i think). It may be the MAF, but I'd sure like to narrow things down before doin' the "crap-shoot" with $150 parts.
    Sounds like a bad MAF. These Bosch MAF's are absolute junk and fail ALL the time. I replaced mine a few weeks ago and the elements were perfect and clean as well.

    BTW there is no actual code specifically for a MAF or any other part.

    At rockauto.com they cost only $114

  9. #8
    bomkok is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    1986cimmeron...thank you very much...excellent information posted there. I just ordered(just received and learnin' how to use) an AutoTap scan tool for the laptop and this info should help greatly.

    Warez...I'm close to breakin' down and buyin a MAF, but I'd like to get a fuel pressure reading first, if i could only figure out where to attatch the guage(damn...wish Haynes or Chilton would put out a manual for this car).


    Anyhow...on preliminary scans, the MAF seems to be charting in parallel with RPM and Throttle Position with a couple anomolies, and after clearing the DTC a couple times, I haven't been able to recreate the P0172 so at least I'm only dealing with the lean condition now, as opposed to conflicting rich/lean DTC's.

    Thanks again...and i will posts final results...sooner or later.

  10. #9
    bomkok is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    Well...MAF sensor cleaned her up and got her through smog-inspection.

    but...now the idle seems pretty low...down around 500rpm...otherwise running good, again.

  11. #10
    AllenPacla is offline Cadillac Owners Fanatic
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    Re: P0171 and P0172 ???

    500rpm i believe is normal for a Catera at idle

  12. #11
    yomincarr is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    Bomkok, are you still having the same problem? I also replaced the fuel filter to no avail. So i took it to my mechanic and he cleaned it up and resealed it (the MAF), said it looked like someone had messed with it before. The code came back on 100 miles later. I just wanted to see if you had any more luck with it before i throw down money on a new sensor.

  13. #12
    TitanCTS's Avatar
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    Re: P0171 and P0172 ???

    I've had the same issue. Replace the MAF and call it a day. Cleaning won't do anything. These are hot wire MAF sensors. The elements may look clean but the circuitry burns up and thats why they fail.

  14. #13
    yomincarr is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    ok, im a college student so i was hoping to avoid dropping that much money...so im guessing its not a fuel pressure issue? auto zone has a test kit i was going to try before getting a new maf.

  15. #14
    CateraMV6's Avatar
    CateraMV6 is offline Cadillac Owners Connoisseur
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    Re: P0171 and P0172 ???

    When you decide its time for a new MAF autozone has them for 72$... good luck.

  16. #15
    truemoparian is offline Cadillac Owners Member
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    Re: P0171 and P0172 ???

    I solved my testing issues with my 99 catera(bult in germany opel plant L81 motor. Fir around $30 bucks on ebay buy a bluetooth ELM27 obdII for android and the TORQUE app is 5 bucks. you can custimize the readouts in realtime display to read current operating values for fuel/intake pressure/vaccuum values and much much more. what it won't do is tell me the voltage draw on a idle air actuator, if anyone knows the operating ohms for gm#90466214 that would be great!

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